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Background/purpose Culture environments play a critical role in stem cell expansion. This study aimed to evaluate the effects of 2,3,5,4′-tetrahydroxystilbene-2-O-b-D-glucoside (THSG) on the proliferation and differentiation of human dental pulp stem cells (DPSCs) in 2-dimensional (2D) and 3-dimensional (3D) culture systems. Materials and methods Human DPSCs were seeded in T25 flasks for 2D cultivation. For the 3D culture system, DPSCs were mixed with microcarriers and cultured in spinner flasks. Cells in both culture systems were treated with THSG, and cell proliferation was determined using a cell counter and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assay. In THSG-treated DPSCs, the genes associated with proliferation, adipogenesis, neurogenesis, osteogenesis, pluripotency, oncogenesis, and apoptosis were analyzed using real-time polymerase chain reactions. Results The spinner flask time-dependently improved cell numbers, cell viability, and expansion rates in THSG-treated DPSCs. In both the T25 and spinner flasks, the messenger RNA (mRNA) levels of proliferation, osteogenesis, and pluripotent-related genes had a significant maximum expression with 10 μM THSG treatment. However, 0.1 μM of THSG may be the most suitable condition for triggering neurogenesis and adipogenesis gene expression when DPSCs were cultured in spinner flasks. Furthermore, the number of oncogenes and apoptotic genes decreased considerably in the presence of THSG in both the T25 and spinner flasks. Conclusion The spinner flask bioreactor combined with THSG may upregulate proliferation and lineage-specific differentiation in DPSCs. Thus, the combination can be used to mass-produce and cultivate human DPSCs for regenerative dentistry.

Periodontitis is an inflammatory disease of the supporting tissues of the teeth induced by periodontopathic bacteria that results in the progressive destruction of periodontal tissues. Treatment of periodontitis is painful and time-consuming. Recently, herbal medicines have been considered for use in treating inflammation-related diseases, including periodontitis. Resveratrol and its derivative 2,3,5,4'-tetrahydroxystilbene-2-O-β-glucoside (THSG), a polyphenol extracted from Polygonum multiflorum, have anti-inflammatory properties and other medical benefits. Here, we highlight the importance of resveratrol and its glycosylated derivative as possible complementary treatments for periodontitis and their potential for development as innovative therapeutic strategies. In addition, we present evidence and discuss the mechanisms of action of resveratrol and THSG on periodontitis, focusing on Porphyromonas gingivalis-induced inflammatory responses in human gingival fibroblasts and animal modeling of ligature-induced periodontitis. We also illuminate the signal transduction pathways and the cytokines involved.

The primary success of implantation is according to osseointegration. The bone-to-implant contact (BIC) % is one of the methods to evaluate the osseointergation. In our study, the mini-pig animal model was used to study the osseointegration in different implant macro-design in early implantation period. Eight mini-pigs were divided into 2 groups and implanted with 2 thread profiles (trapezoidal and square) and 5 thread pitches (0.6, 0.8, 1.0, 1.2, and 1.4 mm) into their jaws. After 8 and 16 weeks, the mini-pigs were sacrificed and the specimen of implant surrounded bone were harvested. The implant surface was detected under scanning electron microscopy (SEM), Masson-Goldner staining (MGS) and immunohistochemical staining (IHC). BIC were obtained under SEM and MGS. Bone formation and maturation were assessed using IHC to detect bone morphogenetic protein-2 (BMP-2) and osteocalcin (OC). The BIC measured for trapezoidal-thread implants with a pitch of 0.8 mm was higher than that of square-thread implants in both the 8- and 16-week groups. The BIC values of the trapezoidal thread profile with a pitch range of 0.6–1.4 mm were not significantly different (P > 0.05) in the 8- and 16-week groups. BMP-2 and OC were detected in both cases, but BMP-2 and OC in the trapezoidal thread group was more regular than the square thread group. The bone in the trapezoidal thread group was more mature. In conclusion, the trapezoidal thread profile with 0.8 mm pitch is the most ideal macro-design for osseointegration.

The objective of this study was to evaluate osseointegration of surface-treated zirconia dental implants using a mini-pig model. Experimentally, zirconia implants with acid-etched surfaces and commercial titanium implants as a control group were introduced into the maxilla and mandible of nine mini-pigs. After 8 and 16 weeks, animals were sacrificed and harvested specimens were examined in terms of resonance frequency analysis, micro-computed tomography, scanning electron microscopy and Masson Goldner staining techniques. The parameters calculated for each section included bone to implant volume (BIV%) and actual bone-implant contact (BIC%). All results were expressed as means ± standard deviations. The different treatment groups were compared using paired t tests. A p

Decision tree (DT) analysis was applied in this cross-sectional study to investigate caries experience in children by using clinical and microbiological data obtained from parent–child pairs. Thirty pairs of parents and children were recruited from periodontal and pediatric dental clinics. All participants were clinically examined for caries and periodontitis by a calibrated examiner. Cariogenic and periodontopathic bacteria examinations were conducted. The Kendall rank correlation coefficient was used to measure the association between data variables obtained through clinical and microbiological examinations. A classificatory inductive decision tree was generated using the C4.5 algorithm with the top-down approach. The C4.5 DT analysis was applied to classify major influential factors for children dental caries experience. The DT identified parents’ periodontal health classification, decayed, missing, filled permanent teeth (DMFT) index, periodontopathic test (PerioCheck) result, and periodontal pocket depth as the classification factors for children caries experience. 13.3% of children were identified with a low decayed, missing, filled primary teeth (dmft) index (dmft < 3) whose parents had a periodontal pocket depth ≤3.7, PerioCheck score >1, DMFT index 2. The DT model for this study sample had an accuracy of 93.33%. Here, parental periodontal status and parents’ DMFT were the factors forming the DT for children’s caries experience.

Background/purpose: The aim of this study was to investigate whether storage of extracted teeth in transportation solution for 24 hours has a negative effect on the cell density and mechanical properties of thawed pulp tissue extracted from frozen intact teeth. Material and methods: Human premolars were kept in transportation solution for 0 hours or 24 hours. For each transportation time, the tested teeth were divided into two experimental groups: teeth that had been frozen in a magnetic programmed freezer (PF, n = 5) and in a traditional freezer at −20°C (TF, n = 5). The tested teeth were then stored at −150°C for 7 days. After thawing, the extracted pulp was subjected to a histological examination and mechanical testing. Results: Storage in transportation solution for 24 hours had no significant negative effects on the histological or mechanical properties of the pulp tissue extracted from the cryopreserved intact teeth. The elastic modulus of pulp from the teeth that had been frozen at −20°C was significantly higher (P

The aim of the study was to investigate the efficacy of the addition of funoran to xylitol chewing gum in dental plaque. In a double-blinded randomized controlled clinical trial, 36 health adults (21–30 years old), who volunteered after informed consent, with >105 colony-forming units/ml mutans streptococci (MS) at baseline, were assigned randomly into one of three parallel study groups: xylitol+funoran gum (group A), sucrose gum group (group B), and control group (no gum have been provided; group C). The pH value, flash weight, and MS of dental plaque were recorded at baseline and after 2 weeks of treatment. A statistically significant reduction (p

This study examines the relationship between the retention force and natural frequency of dental posts cemented with zinc phosphate cement. Forty-two decoronated maxillary incisors were collected and embedded in resin blocks. The 7-mm post spaces were prepared for all test samples prior to cementing the 13-mm Para-Posts with zinc phosphate cement. The natural frequency values and retention forces of the zinc phosphate cement–cemented Para-Posts in various liquid/powder mixing ratios were measured. Thereafter, the natural frequency values of the zinc phosphate cement–cemented posts were continuously detected during ultrasonic vibration. Moreover, both the natural frequency values and the dislodgement forces in response to ultrasonic vibrations were measured for the pretreated post samples. Results showed that the natural frequency values of the posts significantly decreased from 8.8 ± 0.8 to 5.0 ± 0.5 kHz ( P < 0.05) before and after ultrasound treatment, respectively. The natural frequency values and the dislodgement forces of tested posts had a highly linear relationship ( R2 = 0.99, P < 0.05). These findings suggest that natural frequency is a variable for monitoring the stability status of zinc phosphate cement–cemented dental posts.

Introduction Human dental pulp stem cells (DPSCs) have been reported to be useful material for future regenerative medicine. Clinically, cryopreservation of intact teeth can successfully preserve the periodontal ligament for future autotransplantation; however, the effects of cryopreservation procedure on the properties of DPSCs are still unclear. The aim of this study was to test whether DPSCs isolated from cryopreserved teeth can express stem cell–specific markers. Methods In this study, a novel programmable freezer coupled to a magnetic field was used to perform the cryopreservation experiments. The tested DPSCs were isolated from magnetically cryopreserved and non-cryopreserved fresh teeth with an enzyme digestion procedure. The success rate of isolation, growth curves, morphology, stem cell–specific markers, and the differentiation capacity of the isolated cells were evaluated and compared. Results The isolation rate of dental pulp cells from magnetically cryopreserved teeth was 73%. After culture for 5 generations, there was no significant difference in cell viability between cells isolated from magnetically cryopreserved teeth and those isolated from fresh teeth. There were also no visible differences between the 2 groups of dental pulp cells in morphology, expression of stem cell markers, or osteogenic and adipogenic differentiations. Conclusions The results suggest that cryopreserved whole teeth can be used for autotransplantation and provide a viable source of DPSCs.

Background/purpose Poorly crystalline hydroxyapatite was improved so that it has better cell affinity in vitro . We studied the efficacy of a novel resorbable poorly crystalline hydroxyapatite-based biphasic calcium phosphate, BonaGraft, for bone regeneration in vivo . Materials and methods The beagle was used as an animal model, and cylindrical artificial bone defects (3 mm in diameter and 6 mm long) were produced in the alveolar bone. The BonaGraft (ratio of poorly crystalline hydroxyapatite to b-tricalcium phosphate, 60:40) was used to fill in the defect, and unfilled defects served as a control group. At 5, 8 and 10 weeks after the operation, the size of the residual graft and new bone formation were evaluation by a histomorphometric analysis. In a clinical trial, 33 enrolled patients included 15 males and 18 females with ages ranging from 35 to 54 years. The main indications were ridge augmentation ( n = 12), sinus lifting ( n = 2), repair of periodontal disease ( n = 14), and repair of radicular cysts ( n = 5). The clinical outcomes of the surgery were primarily evaluated by clinical radiographs. Results In the animal study, implanting BonaGraft produced greater new-bone formation (74.5% ± 1.0%) at 10 weeks postoperatively than that of the control (40.2% ± 0.3%). BonaGraft particles were gradually resorbed and substituted by bone. The in vivo graft resorption time and bone healing time of 12.1 weeks were mathematically determined by the least squares method. In the clinical test, all patients implanted with BonaGraft reported satisfactory clinical outcomes without major material-related side effects. According to the radiographic pictures, implantation of BonaGraft enhanced bone formation. Conclusion According to the animal study results, BonaGraft has a suitable resorption period and satisfactory outcomes of new bone formation. The clinical study produced high satisfaction with clinical results both objectively and subjectively. For this reason, BonaGraft seems to be an alternative choice for a bone substitute in dental applications.

Stem cell (SC) therapy has a promising future for tissue regenerative medicine. However, because SC technology is still in its infancy, interdisciplinary cooperation is needed to achieve successful clinical applications. Dental SCs have drawn attention in recent years because of their accessibility, plasticity, and high proliferative ability. Several types of dental SCs have been identified, including dental pulp SCs from adult human dental pulp, SCs from human primary exfoliated deciduous teeth, periodontal ligament SCs, and dental follicle SCs from human third molars. Similar to mesenchymal SCs, these dental SCs can undergo self-renewal and have multipotent differentiation ability, but do not have the ethical issues associated with other sources of SCs. Therefore, appropriate preservation procedures for dental SCs and teeth are now needed. Here, we discuss the opportunities for tooth-banking (as it is now clinically feasible and commercially available), the advantages and limitations of current cryopreservation techniques for dental SCs/teeth or tissues, and the current status of tooth banks.

Purpose. To investigate peri-implant alveolar bone changes using periapical radiographs before and after prosthetic delivery in submerged and nonsubmerged dental implants. Methods. Digital periapical films of 60 ITI Straumann nonsubmerged dental implants and 60 Xive Dentsply submerged dental implants were taken before, immediately after, and 12 and 24 weeks after the prosthetic restoration was delivered. Results. The 60-nonsubmerged dental implant group showed mean marginal bone resorption at baseline of 0.10 ± 0.23 mm and 24 weeks later, marginal bone resorption was 0.16 ± 0.25 mm. The submerged dental implant group showed a significantly higher distal marginal bone resorption over the mesial side. Mean marginal bone resorption at baseline was 0.16 ± 0.32 on the mesial and 0.41 ± 0.56 on the distal side. Twenty-four weeks later, it was 0.69 ± 0.69 mm on the mesial and 0.99 ± 0.90 mm on the distal side. Conclusion. First, it was possible to determine that submerged implants had a higher mean marginal bone resorption and less bone-to-implant contact than nonsubmerged implants. And second, the distal side of submerged dental implants presented higher marginal bone loss than the mesial side.

Purpose: To evaluate whether resonance frequency (RF) analysis combined with modal damping factor (MDF) analysis provides additional information on dental implant healing status. Materials and Methods: In in vitro tests, epoxy resin was used to simulate the implant healing process. The RF and MDF values of the implants were measured during the entire polymerization process. Implant stability quotient (ISQ) and Periotest values (PTVs) from Ostell and Periotest devices were used to validate the apparatus. In in vivo experiments, vibrational analysis was performed on 17 dental implants in 12 patients. The RF and MDF values of the tested implants were recorded during the first 10 weeks after surgery. The effects of jaw types and primary stability on MDF healing curves were analyzed. Results: In the in vitro model, the RF values obtained from the apparatus used in this study were similar to those obtained from the Osstell device. Unlike the Periotest healing curve, the MDF curve showed a 1.8-fold increase during the early phase. In clinical experiments, the mean RF values were unchanged during the first 2 weeks and increased continuously until 6 weeks. The corresponding mean MDF value decreased over time and reached 0.045 ± 0.011 at 10 weeks, which is approximately 50% lower than the initial value. Although the RF values of the implants with higher initial frequency remained unchanged during the healing period, the MDF values decreased significantly. Conclusion: Analysis of RF combined with MDF provides additional information on dental implant healing status. MDF analysis can detect changes in the implant/bone complex during the healing period even in implants with higher RF values

The purpose of this study was to explore how wearing, or not wearing, protective gloves affects the efficiency of orthodontists in performing certain orthodontic procedures. Thirty-six volunteers were randomly selected from members of the Taiwan Association of Orthodontists. A visual analogue scale (VAS) was used to determine the degree of convenience subjects felt in performing 11 specified orthodontic procedures, with and without gloves. In addition, the time required to bend round and rectangular archwires and to tie and untie ligature wires was recorded. The results showed that for 10 of the 11 orthodontic tasks there was perceived to be no difference when wearing, or not wearing, gloves. Only when bending a round archwire was there perceived to be a difference. When the four orthodontic procedures were undertaken on a typodont and timed, no significant difference was found between the use of gloves/no gloves.

Resonance frequency analysis (RFA) has been used by several investigators to assess the boundary conditions of dental implants. The goal of the current study was to determine the vibrating behavior of a dental implant under various surrounding bone conditions. A 3D finite element (FE) model of a cylinder-type titanium implant was developed. In this model, the implant was embedded into a cubic section of bone. The model was first validated using a series of modal testing experiments. The effects of bony conditions on the resonance frequencies of the implant were computed with different bone types and bone densities. Our results show that the resonance frequency of the implant with type III surrounding bone decreased linearly (r=−0.996, P

When measuring periodontal disease, various types of equipment for making objective measurements of tooth mobility have been proposed. However, these devices and methodology are insufficient in terms of reliability. An innovative method using vibrational theories to assess the periodontal attachment level of natural teeth is presented in this study.Modal testing technique, a non-destructive and time-saving method, was used for non-invasive and quantitative measurement of the natural frequencies of the upper central incisor in vivo and in vitro. A finite element model was established, and modal testing experiments were simulated to assess the relationship between bone level and teeth.The first dominant natural frequency of healthy human upper central incisors ranges from 710 Hz to 3,360 Hz, with an average of 1,701+/-679 Hz. Both in vitro experiment and finite element simulation showed that lowering of the attachment level causes a significant decrease in the natural frequencies, and a strong relationship (r = -0.99, P0.01) was observed between the frequency and the bone level height.Our results suggested that natural frequency is an important parameter for assessing the periodontal condition and that the modal testing technique is a useful supplemental method for assessing the attachment conditions of the periodontium.

The ability to promote new bone formation of poor crystalline hydroxyapatite (PC-HA) based biphasic calcium phosphate (BCP) bone substitutes were investigated. Various ratios of porous PC-HA/β-TCP (70/30, 60/40, and 0/100) grafts were fabricated. SEM and XRD measurements were performed to study the morphology and crystalline structure. Cylindrical artificial bone defects (3 × 6 mm(2)) were produced in alveolar bone at premolars extraction site and then filled with sterilized bone grafts. Commercial MBCP and unfilled empty defect served as control groups. At 8 weeks postoperation, samples were harvested from each artificial defect site for histological analysis. New bone formation of all the PC-HA/β-TCP groups was significantly greater than that of the empty control group (p

The objective of this study was to investigate the antibacterial, biocompatibility, and mechanical properties of mineral trioxide aggregate (MTA) set using a calcium lactate gluconate (CLG) solution.ProRoot white MTA (WMTA) (Dentsply Tulsa Dental, Tulsa, OK) was used as the control group; MTA-like cement was prepared by mixing Portland cement/bismuth oxide/calcium sulfate (75/20/5) as the experiment group. A solution of 23.1 wt% CLG was used as a hydration accelerant and was compared with deionized water (DDW). Changes in pH values, antibacterial properties, in vitro cell viability, and diametral tensile strength (DTS) of the hydrated cements were assessed.Like WMTA, pH values for the MTA-like cement set using DDW and the CLG solution showed minor but statistically significant differences (P.05). The antibacterial effects of hydrated specimens set by DDW and CLG against Streptococcus mutans assessed with an in vitro tube dilution test showed a significant difference in the early hydration time but no significant difference after 60 minutes (P.05). A mouse osteoblastic cell (MC3T3-E1)-based MTT assay revealed that WMTA set using CLG had significantly higher cell viability than that set using DDW (P.05). The DTS test for hydrated MTA-like cement with different liquids showed a significant difference on day 1 but no statistical difference on day 21.The results suggest that using a CLG solution as the hydration accelerant may enhance the biocompatibility but not compromise WMTA's antibacterial and mechanical properties.

Introduction Mineral trioxide aggregate (MTA) fulfills many of the ideal properties of a root end filling material and repair material for furcal perforation. However, its low cohesive property often makes it difficult to handle. To improve the handling properties of MTA root canal filling materials, MTA-like cement was made, and calcium lactate gluconate (CLG) aqueous solution was used to shorten the setting time and enhance the paste viscosity. Methods CLG solution was prepared by mixing lactic acid, glucono delta lactone, and calcium oxide by wet process. The crystalline property of the CLG powder was characterized by x-ray diffraction. The MTA-like cements were prepared by mixing Portland cement/bismuth oxide/gypsum (75/20/5); ProRoot white MTA (Dentsply Tulsa Dental, Tulsa, OK) was used as a control group. The influence of various liquid phases on initial setting time, handling properties, and pH value were investigated by a Vicat needle, questionnaire of operational hand feel, and pH meter, respectively. Results By using 23.1wt% CLG solutions as a liquid phase, the setting time of white MTA was significantly decreased from 155.5 ± 5.0 to 12.3 ± 2.5 minutes. The pH values for hydrated white MTA with deionized water and 23.1 wt% CLG solutions were 12.29 ± 0.02 and 11.81 ± 0.04 at 72 hours. Conclusions The results suggest that the addition of amorphous CLG-based liquid phase provides improvement in sealing ability as well as clinical manageability of dental filling materials.

The aim of this study was to evaluate the effectiveness of vibrational assessment of the mandible fracture patterns. Measurement of natural frequencies and associated vibrational mode shapes was performed to determine the relationship between the dynamic behavior of the human mandible and incidence of mandibular fractures using both in vitro modal testing and finite element analysis. Our results show that the natural frequencies of the human mandible in dry and wet conditions are 567 Hz and 501 Hz, respectively. The first vibrational mode of human mandible is a bending vibration with nodes located at the mandibular body where bone fracture is less likely to occur. By contrast, high vibration amplitudes were identified in the symphysis/parasymphysis and subcondyle regions where bone fractures tend occur. These findings indicate that the vibrational characteristics of the mandible are potential parameters for assessment of the mechanisms of injury.

The establishment of osseointegration following dental implant placement is a major contributing factor to the clinical success and long-term function of implant-retained prosthesis. Radiographic examination and palpation have been two of the methods often used in clinical assessment for implant stability over the years. However, theses radiographs are two-dimensional and difficult to standardize. The investigation was designed to study the use of resonance frequency analysis in search of the stability of the implant-tissue interface in vitro. Resonance frequency was measured when test implants were embedded in bakelites. The change in stiffness observed during bone healing was modeled by embedding implants in gypsum during the setting period. Our results showed that there was an increase in resonance frequency related to a stiffness increment during osseointegration.

The purpose of this study was to evaluate the possibility of using natural frequency (NF) analysis to detect the attachment loss of periodontal tissue. In this study, 698 anterior teeth were examined by a conventional probing method and also by NF analysis. The teeth were triggered to vibrate with an impulse hammer, and the vibrational response was detected by an acoustic sensor. Our results demonstrate no significant difference in NF values between the upper-lower/left-right quadrants of the tested teeth, although the mean natural frequency value of central incisors with periodontal disease was found to be 1.24 +/- 0.11 kHz which is significantly lower than that of teeth in a healthy condition (1.34 +/- 0.20kHz; p < 0.01). On the other hand, the mean frequency for periodontal disease involving canines (1.28 +/- 0.09 kHz) was also significantly lower than the corresponding value for healthy analogs (1.35 +/- 0.17 kHz; p < 0.05). These results suggest that NF analysis appears to be an effective method for assessing the periodontal condition of anterior teeth. Moreover, since this method is noninvasive, nondestructive, and necessitates minimal tooth contact, it can serve as an effective method for the early quantifiable testing and prevention of periodontal disease.

AIM: Our goal was to investigate the relationship between clinical status and the presence of carious or periodontal pathogens among parent-child familial pairs. Clinical practices of risk assessment with consideration of familial pathogen interaction might reduce the need for therapy, improve patient outcomes, and ultimately reduce oral disease burden. MATERIALS AND METHODS: In this study, we enrolled 30 parent-child pairs, with the children exhibiting complete deciduous dentition or mixed dentition with only permanent first molars. Clinical statuses were evaluated using caries and periodontal disease indicators, including the sum of decay and the number of missing or filled teeth (DMFT) for adults, decay, extraction caused by dental disease, and filled teeth (deft), for children, probing depth, and plaque control record (PCR). Supra- and sub-gingival bacteria were determined based on semi-quantitative measurements of microbial infection by using data from the Dentocult(®) SM test (caries-related organisms) and the PerioCheck(®) test (periodontal disease-related organisms). RESULTS: No statistically significant relationship was detected between the prevalence of periodontal pathogens and that of cariogenic pathogens in the oral cavity. However, the clinical status of caries (DMFT) was negatively correlated with the clinical status of periodontal disease (pocket depth) in parents who were infected with dominant periodontal pathogens (r = -0.59, p

The bionator is one of the most commonly used functional appliances in treating Angle Class II division 1 malocclusions. However, the original type of bionator often causes lower incisor flaring and is limited in cases with mild crowding. There is little published literature on treating Angle Class II division 2 malocclusions using bionators. Our group suggested some modifications to the original-type bionator, including addition of an anterior resin cap, upper and lower labial bows, an expansion screw and a posterior resin wedge, to attempt to overcome limitations of the original design. This article shows our results on two male patients, one with an Angle Class II division 1 malocclusion with a large overjet and the other with an Angle Class II division 2 malocclusion. The treatment was completed using a newly modified bionator with no other fixed appliance and resulted in a decrease in facial convexity, a reduced overjet and overbite, ideal interincisal relationships, and a harmonious profile.

Background/PurposeAssessing periodontal conditions has always been a concern for dental researchers. In this study, we evaluated the potential of a natural frequency (NF) analysis to detect the health status of natural human canine teeth.Materials and methodsThree-dimensional finite element models of the human maxillary canine were constructed. NF values of the canine model were calculated with one-, two- and three-sided vertical bone loss.ResultsBy simulating a modal testing experiment, the NF value for a healthy canine was found to be 2581 Hz. As the bone level was lowered, a strong linear relationship between the frequency and attachment level was demonstrated in all three models. Results from this study demonstrated that the change in the NF was < 12% in canines with a one-sided defect when the bone level varied by 10 mm from the cementoenamel junction. However, when a three-sided bony defect was simulated, the change in NF ranged from 20% to 60%.ConclusionThis study demonstrates that the NF of the human canine decreases with various degrees of periodontal bone height loss.

Background/purpose: The aim of this study was to examine the effects of the time period between tooth extraction and the freezing procedure on pulp cells in frozen intact teeth of rats. Material and methods: In total, 120 incisors from 30 rats were extracted and kept in transportation solution for 0 hour, 12 hours, and 24 hours. The tested teeth were divided into 2 experimental groups, where the extracted incisors were first frozen in a magnetic-programmed freezer (PF) or a traditional −20°C freezer (TF). The tested teeth were then stored at −150°C for 7 days. Incisors extracted from the opposite side of the same rat were treated as the non-frozen control. After thawing, the pulp was extracted and dissected. Hematoxylin and eosin staining was performed to observe the cell distributions. Cell densities in the odontoblast region and cell-rich zone were calculated using an optical microscope. Results: When samples were immediately frozen after extraction, the cell density of odontoblastic cells was higher in the PF group compared with analogs which were frozen in the −20°C freezer (P